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用机载粒子测量系统(PMS)对新疆冬季一次系统降雪进行了探测。结果表明:枝状雪晶间碰撞攀附形成雪团,一方面使直径大于3300微米的雪晶数浓度明显增加,另一方面又使直径700—3300微米的雪晶数浓度明显减小,同时引起了枝状雪晶的折裂繁生,使冰晶(18≤D<3400微米)数浓度平均增加35%,雪晶数浓度平均增加10%。 相似文献
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前言 新疆冬季低云是在高压底部、低层逆温下形成的层云(St)和层积云(Sc)。它分布于天山北麓一带。低云不厚,一般仅几百米,但维持时间长,可数日不消散。这种低云往往是过冷水云,有时有微量降雪,雪花形状多是枝状、星状或它们碰连形成的雪团和米雪。低云中过冷态云粒子粒径小但数浓度高,这对水平、垂直能见度影响很大,因而严重地影响了航空、地面交通的正常运行。对农作物生长也带来了很大危害。因此研究低云形成、维持、消散的动力学特征,云中微物理过程,人工影响途径和方法,有着重大的实际意义。 对新疆低云的飞机探测始于1978年冬 相似文献
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众所周知,雾作为一种视程障碍现象,对航空、航海等交通运输的安全威胁很大。据统计,全世界雾日中暖雾占95%,因此,消暖雾的研究十分迫切和重要。二十多年来,国内外采用了多种方法进行消雾试验。播吸湿粒子消雾是其中的一种,此法从科学原理上是符合的,但是,如何在指定时间和地点消雾这个工程问题尚未解决。不仅如此,据国内一系列试验表明:消雾效果除与吸湿粒子的吸湿性能、用量、颗粒大小有关外,还取决于雾形成后的气象条件和雾的特性。当雾层不太厚、雾中风速不大、雾滴谱比较窄时,只要吸湿粒子用量、颗粒大小适当,消雾效果还是明显的。本文仅介绍用吸湿粒子消雾用量的计算方法和应用实例。 一、消雾原理和用量上下限 吸湿粒子消雾是通过潮解、稀释过程中强烈吸湿,大量消耗雾层中水汽,迫使雾滴急剧蒸发,吸湿粒子迅速长大并掉出消雾空间,使消雾空间光学切面 相似文献
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夏蘩 《高原山地气象研究》2020,40(4):22-29
利用FNL再分析资料和中尺度数值模式输出的高分辨率资料,分析了2016年6月30日~7月1日发生在重庆的一次低涡暴雨过程的环流背景、水汽输送特征和收支状况、云物理降水机制。结果表明:受500hPa短波槽和700hPa低涡共同影响,以及孟加拉湾和南海的暖湿气流持续输送,为此次低涡暴雨的发生、发展提供了有利的条件;南边界的水汽输入通量对整个暴雨过程中水汽的贡献最大,东边界次之。另外,降水发展不同区域不同时段,云物理降水机制都存在显著差异。渝西降水前期和后期,均为混合相降水;渝东北降水前期云系以冷云为主,后期以暖云降水为主。 相似文献
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This paper uses the ARW-WRF model to carry out a numerical simulation of a warm-sector heavy rainfall event over southern China on the 22–23 May, 2014. A composite analysis method was used to analyze the evolution process and structural features of the convective cells on a convection line during this rainfall event. This analysis identified three stages: (1) Stage of activation: the equivalent potential temperature surfaces as lower layers start to bulge and form warm cells and weak vertical convective cloud towers which are subject to the impact of low-level warm moist updrafts in the rainfall sector; (2) Stage of development: the warm cells continue to bulge and form warm air columns and the convective cloud towers develop upwards becoming stronger as they rise; (3) Stage of maturity: the warm air columns start to connect with the stable layer in the upper air; the convective cloud tower will bend and tilt westward with each increasing in height, and the convection cell is characterized by a “crescent-shaped echo” above the 700hPa plane. During this stage the internal temperature of the cell is higher than the ambient temperature and the dynamic structural field is manifested as intensive vertical upward movement. The large-value centers of the northerly and westerly winds in the middle layer correspond to the warm moist center in the cells and the relatively cold center south of the warm air column. Further analysis shows that the formation of the “crescent-shaped” convective cell is associated with horizontal vorticity. Horizontal vorticity in the center and west of the warm cell experiences stronger cyclonic and anticyclonic shear transformation over time; this not only causes the original suborbicular cell echo shape to develop into a crescent-like shape, but also makes a convection line consisting of cells that develop to the northwest. 相似文献
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